Preimplantation development is characterized by cell proliferation, differentiation, and differential gene expression, and cAMP can regulate these processes in other systems. Although cAMP metabolism and function have been studied in mouse oocytes, a paucity of such information exists for the preimplantation mouse embryo. We have recently demonstrated that adenylate cyclase activity develops during the morula to blastocyst transition of mouse embryos and that activation of the cAMP-dependent protein kinase inhibits both cleavage of 1-cell embryos and transcriptional events in the 2-cell embryo. These studies will be pursued by determining the effect of perturbing cAMP metabolism and protein phosphorylation on cleavage at other stages preimplantation development and compaction and correlating these perturbations in development with changes in the patterns of total and phosphoprotein synthesis, as assessed by two- dimensional gel electrophoresis. In addition, the effect of gyno-, androgenotes, and nuclei of later cleavage stage embryos transferred to enucleate zygotes will be analyzed to see if the developmental abnormalities intrinsic to these embryos are manifested at the level of phosphoprotein synthesis and appearance of adenylate cyclase. The trophectodermal cells of the blastocyst constitute a polarized, fluid transporting epithelium, which in other systems, is stimulated by cAMP. We have shown that cAMP stimulates expansion of the blastocoel cavity and plan to pursue this observation by determining if cAMP stimulates uptake of 22Na by cavitating blastocysts. Lastly, we will determie if embryos synthesize prostaglandins and if embryo adenylate cyclase is activated by these prostaglandins. Prostaglandins may serve as activators of embryo adenylate cyclase and thus may provide a stimulus for initiating blastocoel cavity formation that is essential for further development. Results of these studies will provide a wealth of fundamental information regarding the role of protein phosphorylation in preimplantation development and the mechanism of action of cAMP in blastocoel formation.